Gentlemen, Here are my current conclusions on this build. I am going to get a geiselle trigger, the SSA-E model listed for AR-15's. Daniel defense looks like it is out of lpk's, also they don't have one listed without a trigger. I would rather not pay for a trigger that I am never going to use. Can anyone recommend a heavy duty lpk that might not include a trigger? Also, the Fulton Armory M110 service rifle upper looks like it will suit my needs. As far as the receiver extension, I am looking at rifle length stuff. I read somewhere on here that armalite buffer springs are the best, are they worth ordering on their own? Optics budget is less than 500, and can anyone recommend some quality iron sights? Happy Shooting